Method of extruding elongated members



July 24, 1956 H. HORN 2,755,926 METHOD OF EXTRUDING ELONGATED MEMBERSFiled Jan. 8, 1953 2 Sheets-Sheet 1 INVENTOR. f/f/A Z fiOR/V July 24,1956 H. HORN 2,755,926 METHOD OF EXTRUDING ELONGATED MEMBERS Filed Jan.8, 1953 2 Sheets-$heet 2 INVEN TOR. HE/A Z HORN EEQW W 2,755,926 METHDDF EXTRUDING ELONGA'I-TED MEMBERS Application January 8, 1953, Serial No.330,284 6 Claims. (Cl 207---') Elongated extruded members such. as rods,tubes, structural and other shapes have customarily been manufacturedheretofore by means of ram extrusion presses. The material of which theextruded member is to be made is inserted in the form of a solid billetinto the container or receiver of the press and extruded through a dieunder the pressure exerted by a ram which is usually hydraulicallyoperated. Even though the billet itself is freeof air and gas inclusionsit is frequently ditficult to obtain a blister-free product because ofthe air inclusions which take place during the extrusion process becauseof the initial radial expansion of the billet by the ram pressure. Thisradial expansion presses the billet material solidly against the wall ofthe receiver so that air is entrapped which forms blisters in theextruded product. The blistering effect is most pronounced when theinitial radial expansion takes place at the ram end of the billet sothat a maximum amount of air is entrapped. Such blistering isparticularly obnoxious when the extruded member is a sheath of aluminumor other metal or alloy having a higher melting point than lead such asis used to protect an electrical cable wherein the imperviousness tomoisture is of particular importance.

Objects of this invention are to provide a method for making extrudedmembers substantially free from air inclusions, which is particularlyadapted for making sheathing for electrical cables, which can be carriedout without modification of present equipment, which does not requirespecial tools or skills, and which advances the art generally.

These and other objects will be apparent from the following detaileddescription of the process which refers to the drawings wherein:

Figs. la, 1b, 1c and 1d are diagrammatic longitudinal sectional views ofa press for making an extruded member having a solid cross section;

Fig. 2 is an isometric view of a billet for the press shown in Fig. la;

Fig. 3 is a diagrammatic longitudinal sectional view of a press formaking a hollow extruded member; and

Fig. 4 is an exploded isometric view of a billet for the press shown inFig. 3.

In Fig. la are diagrammatically shown the essential elements of anextrusion press such as is well known in the art so that they need notbe described further other than to say that 10 represents the receiverhaving a bore wherein is reciprocatingly disposed a hydraulicallyoperated ram 12, the end of the bore opposite that through which the ramenters being closed by an apertured die 14 of a Wearresistant material.When the above described press is used in the conventional manner, theram 12 is withdrawn from the bore of the receiver 10 and the bore loadedwith a cylindrical billet having a diameter slightly less than the boreand a length great enough so that it substantially fills the bore. Theram then is brought into contact with the end of the billet exerting ahigh pressure thereupon so that the material of the billet flows outthrough the aperture in the die 14.

States Patent 0 As mentioned heretofore, with a long billet the endthereof nearest the ram expands first in a radial direction trapping aconsiderable amount of air along the length of the billet which causesblisters and inclusions in the extruded product. I overcome defectscaused in the above manner by first inserting in the bore of thereceiver 10 a relatively short billet B whose length is preferably lessthan one and one-half its diameter as is shown in Fig. la. The secondstep is to expand the billet in a radial direction by operation of theram 12, as is shown in Fig. 1b, the short length of the billet reducingthe amount of air trapped during such radial expansion. Successive shortbillets B, B", B', are sequentially inserted and expanded radially bythe ram 12, as is shown in Fig. 10, untilthebore of the receiver 10 isfilled whereupon the material of the billets is extruded in an elongatedmember M which minimizes the air blisters and inclusions, as is shown inFig. 1d.

The above described process is particularly applicable to the extrusionof material such as aluminum alloys for electrical cable sheathingwherein the imperviousness to moisture and water is of the greatestimportance. As is shown in Fig. 3,. an insulated electrical conductor Cis fed through a hollow mandrel 16 so that the end thereof passesthrough the aperture in the die 14. The mandrel 16 which is relativelystationary with respect to the die 14 and the receiver 10, passesthrough an aperture in the ram 18. It is therefore necessary to providebillets in the shape of an annulus or ring to accommodate the mandrel 16rather than cylindrical billets B such as were used in the embodimentshown in Figs. la to 1d. To facilitate inserting of the billets in thebore of the receiver 10, each billet is preferably provided with two ormore radial cuts so that it is divided into several sectors as is shownin Fig. 4.

The process for making hollow members or sheathing is carried out in amanner analogous to that described heretofore. The receiver 10 ischarged by inserting the sectors which comprise one of the billets S andexpanding the inserted billet by means of the ram 18 so that the air inthe interstices between sectors and between the sectors and the receiverwall can escape as the billet is expanded. Succeeding billets S areinserted one at a time and expanded until the receiver bore is filled.The ram 18 then is used to force the billet material out through thespace between the die 14 and the mandrel 16 so that a sheath is formedwhich surrounds the cable C as it is fed from the mandrel at the samerate that the sheath is extruded.

I claim:

1. The method of extruding an elongated member substantially free fromgas inclusions comprising the steps of inserting a plurality of shortbillets in the receiver of an extrusion press in the number requiredsubstantially completely to fill the receiver, expanding each of thebillets by the operation of the press ram before the succeeding billetis inserted to bring the periphery of the inserted billet into contactwith the wall of the receiver, and after the receiver is filledoperating the ram to extrude the material of the billets through the dieof the press to form the elongated member.

2. The method of extruding an elongated member substantially free fromair inclusions comprising the steps of inserting in the receiver of anextrusion press a billet whose length does not substantially exceed itsdiameter by more than one and one-half times, deforming the billet in aradial direction by the operation of the ram of the press until theentire periphery of the billet is in contact with the wall of thereceiver, withdrawing the ram from the receiver, repeating the abovedefined steps to insert and deform a plurality of billets in the numberrequired substantially completely to fill the receiver, and subsequentlyoperating the ram to extrude the material of the billets through the dieof the press to form the elongated member.

3. The method of extruding a hollow elongated member substantially freefrom gas inclusions comprising the steps of inserting about the mandrelin the receiver of an extrusion press an annular billet whose lengthdoes not sub stantially exceed its outer diameter by more than one andone-half times, deforming the billet in a radial direction by theoperation of the ram of the press to bring the outer and innerperipheries of the billet into contact with the walls of the receiverand mandrel respectively, repeating the above defined steps to insertand deform a plurality of billets in the number required substantiallycompletely to fill the receiver, and subsequently operating the ram toextrude the material of the billets through the die of the press to formthe elongated member.

4. The method of extruding a hollow elongated member according to claim3 including the further step of dividing each billet into severalsectors to facilitate the insertion thereof in the receiver.

5. The method of extruding a sheath for an electrical cablesubstantially free from air inclusions comprising the steps of insertingabout the hollow mandrel of an extrusion press an annular billet Whoselength does not substantially exceed its outer diameter by more than oneand one-half times, deforming the billet in a radial direction by theoperation of the ram of the press to bring the outer and innerperipheries of the billet into contact with the walls of the receiverand mandrel respectively, repeating the above defined steps to insertand deform a plurality of billets in the number required substantiallycompletely to fill the receiver, and subsequently operating the ram toextrude the material of the billets through the die of the press to formthe sheath about the wire as it is pulled through the mandrel.

6. The method of extruding a sheath according to claim 5 including thefurther step of dividing each billet into several sectors to facilitatethe insertion thereof in the receiver.

References Cited in the file of this patent UNITED STATES PATENTS529,215 Tatham Nov. 13, 1894 571,332 Bicheroux Nov. 17, 1896 1,654,526Brown Jan. 3, 1928 1,720,722 Dean July 16, 1929 2,639,809 Perry et alMay 26, 1953 FOREIGN PATENTS 415,359 Great Britain Aug. 23, 1934 657,185Great Britain July 12, 1951 873,080 France June 29, 1942

1. THE METHOD OF EXTRUDING AN ELONGATED MEMBER SUBSTANTIALLY FREE FROMGAS INCLUSIONS COMPRISING THE STEPS OF INSERTING A PLURALITY OF SHORTBILLETS IN THE RECEIVER OF AN EXTRUSION PRESS IN THE NUMBER REQUIREDSUBSTANTIALLY COMPLETELY TO FILL THE RECEIVER, EXPANDING EACH OF THEBILLETS BY THE OPERATION OF THE PRESS RAM BEFORE THE SUC-